We use an automatic one. Speak to June at Gaps Water.
I only have two vans though and a 1000 litre static ibc . I wasn't regenerating often enough before so bought a bigger vessel for the softener resin. You don't wanna be regenerating mid fill as I ideally needed to, not unless you go twin automatic like I think Lee Pryor has. Then you're talking big money I think. Also you want a nice big brine tank to hold a fair few bags of salt. Saves constantly filling the brine tank. Basically I need to backwash/regenerate the resin every ibc tank of pure.
And it does bring down your tds slightly no matter what anyone says. Mine comes out of RO at 2 or 3ppm after a regen but more like 10ppm if I haven't regenerated. Tap TDS is around 256 last time I checked some time back.
A lot of people think they're a waste of time or uneconomical because of buying the salt but I definitely think they're worth it.
Hope that helps.